What does the term "runway incursion" refer to?

The term "runway incursion" specifically refers to an unauthorized entry onto a runway by an aircraft, vehicle, or person. This situation poses significant safety risks as it can lead to potential collisions with aircraft that are either taking off or landing. The definition encompasses not only aircraft that may mistakenly enter the runway but also ground vehicles, which might inadvertently be on the runway without clearance.

Contextually, understanding runway incursions is crucial for maintaining safe operations at airports, which often have multiple aircraft and vehicle movements occurring simultaneously. While other options like collisions during taxiing, missed approaches, and delays in takeoff clearance are relevant scenarios in aviation, they do not accurately characterize the specific meaning of a runway incursion as defined by aviation safety protocols.